The present invention relates to an information processing apparatus to be connected to a digital communication line to communicate data, and in particular, to a technology effective to control the life of batteries in a battery-driven hand-held information processing apparatus including a digital communication line interface circuit to be connected to a network such as a local area network to communicate data.
In use of conventional information processing apparatuses or processors, a plurality of information processors are connected to a network such that various data items are communicated between the plural information processors.
The information processor connected to the network to communicate data as above includes a digital communication line interface circuit to be connected to the digital communication line.
For the interface above, there exists recently a tendency that the transfer speed is considerably improved and the power consumption is conspicuously increased due to the direct connection to a high-speed bus.
Presently, when a digital communication line interface circuit is installed in a battery-driven hand-held information processor, the ratio of power consumption of the interface circuit takes quite a large value in the overall power consumption of the information processor.
In the case of the battery-driven information processor, the digital communication interface circuit is used primarily in an office environment and, hence when the apparatus is being carried about and is driven by batteries, the interface circuit is not connected to a digital communication line such as a network in many cases. Therefore, in general, when the information processor is being carried about, the interface circuit is not used.
Consequently, when the battery-driven information processor is being carried about and is driven by batteries, it can be considered to elongate the battery drive time by stopping the interface circuit not used. However, in the conventional information processor, to stop only the line interface circuit when the line is not used, there arises a difficulty. Namely, it is necessary to provide a sleep signal and a circuit or the like to relate the signal to a link signal.
On the other hand, in JP-A-61-173578, there has been described a communication start/end scheme for use with an apparatus in which a telephone line is shared between a telephone set and a data terminal, the method remarkably lowering power consumption of the apparatus and simplifying the function to identify a call termination and the function to monitor the end of call.
According to the apparatus of JP-A-61-173568, a logic to distinguish a telephone call from a data communication and a logic to monitor the end of call are disposed in a read-only memory (ROM), and the apparatus is entirely powered at call termination such that the start or end of call is awaited according to the logic in association with activation of the ROM to interrupt power, only excepting the line interface section, so as to set the apparatus to a standby state.
The present inventors have considered the prior art, and have found the following problems.
That is, in the conventional information processor, since it is difficult to stop only the digital communication line interface circuit when the digital communication line is not used, there has been a problem that the power consumption of the interface circuit cannot be minimized even when the information processor is used for a purpose other than for digital communication.
Furthermore, when the conventional information processor is driven by batteries, the interface circuit continuously consumes a large amount of power even when the digital communication line is not used, which raises a problem of a short battery life and a minimized battery drive time.
Additionally, in the conventional information processor, even when the digital communication line is not used, the digital communication line interface circuit continuously uses the hardware resource to establish an interruption signal, an address space, and the like, which therefore results in a problem of restriction in expandability of the information processor.
On the other hand, in the conventional communication start/end method of JP-A-61-173568, there are effected reduction of power consumption of the processor when externally accessing a host via a telephone line, and simplification of the function to identify a call termination and the function to monitor the end of call, which leads to a problem that power cannot be turned on or off in response to an access from the host side.